The development of cell therapies is the focus of investigations for the treatment of numerous indications with currently unmet needs. Such therapies administered as a cell suspension ideally require the use of a vehicle that is compatible with the cells, non-toxic to the recipient, and suitable for storage of the therapy for a sufficient time prior to and during administration.
Preservation of cell therapies in ambient or hypothermic (2° C. to 8° C.) conditions is necessary for early phase clinical trials of allogeneic therapies. It is also more likely to be used for autologous cell therapies, which utilize patients' own cells as a starting material.
Cryopreservation is likely to be necessary for long-term storage of cell therapies prior to administration. Later phase multi-centre trials will require substantially longer storage times than can be achieved using hypothermic storage, as the therapeutic cell product is likely to be manufactured centrally and distributed over a number of months. Ultimately, post-authorisation manufacture of cell therapy products will necessitate storage for numerous years.
The use of the cryoprotectant dimethylsulfoxide (DMSO) has great utility in preserving cells in liquid nitrogen freezers (˜−195° C.). DMSO is a member of the class of dipolar aprotic solvents, which also includes dimethylformamide, N-methyl-2-pyrrolidone and hexamethylphosphoramide, and is the most common cryoprotectant used in the manufacture and banking of cell therapies. However, this solvent is toxic to the cell product and subsequently to the treated patient (Hubel, 2001; Sauer-Heilborn et al., 2004). For example, in bone marrow transplants, almost all patients receiving DMSO-cryopreserved cells suffer side effects and a small number experience serious complications. Direct effects during infusion and delayed-onset side effects have been observed in a dose dependent manner. The effects described occurred when the cell formulation was administered systemically and so any formulation ingredients are diluted and widely distributed. In contrast, administration via direct injection into tissue (for example, intracranial, intramuscular or intracardiac administration) would increase local toxicity effects. Methods to remove the DMSO content from cryopreserved cells have reduced DMSO-related complications and side-effects (Syme et al., 2004). However, these processes were inefficient with as little as 60% of the cell product recovered (Calmels et al., 2003).
The use of glycerol and trehalose has been shown to be effective in the storage of cryopreserved sperm (Storey et al., 1998), however this method has been found to be ineffective with different cell types.
Previous formulations of cells for administration have relied on cell culture medium and modified saline solutions. Although these formulations are suitable for administration, they do not preserve the viability of the cell product for more than a few hours. This precludes them from clinical studies, wherein the time taken to release the product for clinical administration, followed by transit, and the potentially lengthy process of implantation (up to 9 hours in total) may render the cells non-viable. Therefore there is necessity to increase the shelf-life of these products beyond this 9 hour period in order to overcome the immediate obstacles of early clinical trials. In addition, in order for a cell therapy product to be commercially viable, a much longer storage strategy is needed.
The excipient HypoThermosol®-FRS (HTS-FRS) (BioLife Solutions, Inc) is a hypothermic storage solution that was initially developed as a perfusate to be used during cardiac arrest coupled with profound hypothermia, in order to minimise ischemic injury. HTS-FRS is a commercially-available formulation designed to mediate the level of post-storage necrosis and apoptosis in cells undergoing prolonged periods of hypothermic (2° C.-10° C.) preservation.
U.S. Pat. No. 6,921,633 discloses a method of preserving a cell, tissue or organ by contacting said cell, tissue or organ with a hypothermic storage solution comprising a composition that inhibits apoptosis and a sufficient concentration of vitrification composition to vitrify said solution.
U.S. Pat. No. 6,632,666 discloses a gel-based composition for use in the nanothermic, hypothermic or cryopreservative storage and transport of cell samples comprising HTS-FRS and a gelling agent.
WO2005/009766 discloses a pharmaceutical composition comprising liver cells, HTS and DMSO which can be stored at cryothermic temperatures.
Following storage of these compositions at hypothermic or cryothermic temperatures, substantial processing of the cell therapy product is required in order to remove the toxic cryoprotectants prior to administration. This may lead to additional release testing which is both burdensome and costly.
Therefore, there is a need for compositions and formulations which provide an alternative to DMSO and which can be stored at cryothermic temperatures and used as a vehicle for direct administration of cell therapies.